If I’m in the US, and my friend is in Europe with their US phone, from my phone’s perspective is it considered international calling if I dial their US number while they’re away, or if they call me from there?
It’s not an international call in either direction for you. You won’t see any additional charges from Republic beyond monthly plan fees. For your friend, it’s entirely different and dependent upon their service provider. By the way, Republic phones can receive calls from international numbers other than U.S. and Canadian numbers without charge beyond monthly plan fees but cannot make them.